This invention relates generally to rod or bar rolling mills wherein after the rolling operation, the elongate mill product is preliminarily formed into rings which are finally collected into large cylindrical coils. The invention is concerned in particular with an apparatus employed in the collection of such rings into coils.
One known coil forming device is shown in U.S. Pat. No. 3,439,882. This type of device employs four mutually perpendicular axially fixed mandrels supported on a central hub. The hub is rotatably indexed to bring each mandrel to an upstanding position at a collecting station where rings are received axially thereon from an overlying delivery device and accumulated in coil form. Thereafter, by rotatably indexing the hub through another 90.degree., the loaded mandrel is brought to a horizontally disposed position at a discharge station on one side of the hub, while another empty mandrel is moved into an upstanding operatative position at the collecting station. With this type of device, there is always one empty mandrel protruding downwardly from the hub in opposed relationship to the operatively positioned upstanding mandrel at the collecting station. One decided drawback associated with this type of arrangement is the necessity for providing a large well or pit beneath the hub to accommodate the mandrels as they rotate into and out of their downwardly protruding positions. The excavation and foundation costs associated with providing such pits contribute markedly to the high costs of the equipment.
Another known prior art device is disclosed in U.S. Pat. No. 3,737,050. Here, a pair of axially fixed mutually perpendicular mandrels are rotated about an inclined axis which bisects the angle defined by the mandrel axes. Although this type of arrangement substantially minimizes excavation costs by maintaining the path of mandrel travel about mill floor level, this advantage is to a large extent offset by a number of other disadvantages. For example, because the inclined rotational axis of the hub bisects the angle formed by the mandrel axes, a large tipping moment is produced each time a full coil is transferred from the coil forming station to the discharge station. With relatively heavy coils which frequently weight 6,000 lbs. or more, this tipping moment produces severe stresses which in turn make it necessary to employ extremely heavy housing shafts and bearings. This translates into high capital costs.
Another drawback with this type of equipment stems from the fact that the somewhat conical rotational path of the mandrels makes it difficult to employ a cage or other like structure to radially confine the rings as they accumulate in coil form at the coil forming station. Thus, in order to produce a coil having the desired substantially uniform cylindrical shape, the rings must be relatively tightly packed around the mandrels. When such coils subsequently are stripped from the mandrels, the frictional contact between the inner ring surfaces and the mandrels sometimes damages the rings.
Finally, neither of the above-described prior art devices allows the mandrels to be axially raised above their normal path of rotation into closer proximity to the overlying ring delivery device. Under certain circumstances, depending on the type of ring delivery device being employed. if the gap between the mandrel upper ends and the ring delivery device is too great, instead of being axially received around the mandrels the rings can "hang up", causing a malfunction which seriously disrupts the operation of the apparatus.